Get the target field index when transitioning.

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1426 matching lines @@
   if (transition == TransitionArray::kNotFound) return false;
   PropertyDetails target_details = transitions->GetTargetDetails(transition);
   if (target_details.type() != FIELD) return false;
   if (target_details.attributes() != NONE) return false;
   Handle<Map> target(transitions->GetTarget(transition));
   JSObject::AddFastPropertyUsingMap(object, target);
   return true;
 }
 
 
+int JSObject::LastAddedFieldIndex() {
+  Map* map = this->map();
+  int last_added = map->LastAdded();
+  return map->instance_descriptors()->GetFieldIndex(last_added);
+}
+
+
 ACCESSORS(Oddball, to_string, String, kToStringOffset)
 ACCESSORS(Oddball, to_number, Object, kToNumberOffset)
 
 
 byte Oddball::kind() {
   return Smi::cast(READ_FIELD(this, kKindOffset))->value();
 }
 
 
 void Oddball::set_kind(byte value) {
@@ skipping 4076 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_